Domestic Voltage Stabilizer’s Transformer Humming Normalised
This D V S was on my bench work with complaint of loud humming and output voltage showing letter H. I opened the case and did visual checking. I did observe a bulged e cap, which I did change. When I on the stabilizer, problem same.
For your information, when stabilizer shows H at output voltage it means there is high voltage input than what the stabilizer is rated for. So what is the cause of this problem? Got info from Google it may be caused by defective relay, so checked on the relays, all are in good condition.
Checked on other components: e-caps, diode, resistors, transistors, all good. So I decided to do voltage test on the transformer. On transformer it is indicated secondary output voltages.
When I did check transformer voltages, to my surprise they were all higher then what is rated on transformer (300+Voltages) and the voltage primary input to transformer was also more than 300V, (national grid voltage is 220V.)
I guess this is why transformer was humming loudly. So I focus my attention on input voltage circuit. On this circuit, I found two non-polar caps defective: 105/630V and 104/275V.
Since I don’t have exact cap, I just replaced the two caps with 105/400V each.
Connect all things together and power On, LOL stabilizer works perfectly. This is the finished repaired work.
This article was prepared for you by Imoudu Onwumah from Nigeria. He is 62 years old and has just 3 years experience in electronics repairs. I started career in hotel industry as a chef, but then I was doing repairs only in electrical repairs as a hobbyist. In 2018, I decided to learn about electronics which through Jestine’s electronics e-books and holding my hand, am an electronics techie today.
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Note: You can read his previous article on UNI-T Digital Multimeter Faulty From Time Of Purchase